Nebulized curcumin protects neonatal lungs from antenatal insult in rats

Rationale: Intrauterine growth restriction (IUGR) increases the risk of bronchopulmonary dysplasia (BPD), one of the major complications of prematurity. Antenatal low-protein diet (LPD) exposure in rats induces IUGR and mimics BPD-related alveolarization disorders. Proliferator-activated receptor (PPARg) plays a key role in normal lung development and was found deregulated following LPD exposure. Objectives: Investigate the effects of nebulized curcumin, a natural PPARg agonist, to prevent IUGR-related abnormal lung development. Methods: We studied rat pups antenatally exposed to an LPD or control diet (CTL) and treated with nebulized curcumin (50 mg/kg) or vehicle from postnatal (P) days 1 to 5. The primary readouts were lung morphometric analyses at P21. Immunohistochemistry (P21) and microarrays (P6 and P11) were compared within animals exposed to LPD versus controls, with and without curcumin treatment. Results: Quantitative morphometric analyses revealed that LPD induced abnormal alveolarization as evidenced by a significant increase in Mean Linear Intercept (MLI) observed in P21 LPD-exposed animals. Early curcumin treatment prevented this effect and two-way ANOVA analysis demonstrated significant interaction between diet and curcumin both for MLI (F(1,39)=12.67,p=0.001) and Radial Alveolar Count at P21 (F(1,40)= 6.065, p=0.0182). Immunohistochemistry for FABP4, a major regulator of PPARg pathway showed a decreased FABP4+ alveolar cell density in LPD-exposed animals treated by curcumin. Transcriptomic analysis showed that early curcumin significantly prevented the activation of pro-fibrotic pathways observed at P11 in LPD-exposed animals. Conclusion: Nebulized curcumin appears to be a promising strategy to prevent alveolarization disorders in IUGR rat pups, targeting pathways involved in lung development.

Former-preterm lambs have persistent alveolar simplification at 2 and 5 months corrected postnatal age

Preterm birth and mechanical ventilation (MV) frequently lead to bronchopulmonary dysplasia, the histopathological hallmark of which is alveolar simplification. How developmental immaturity and ongoing injury, repair, and remodeling impact completion of alveolar formation later in life is not known, in part because of lack of suitable animal models. We report a new model, using former-preterm lambs, to test the hypothesis that they will have persistent alveolar simplification later in life. Moderately preterm lambs (~85% gestation) were supported by MV for ~6 days before being transitioned from all respiratory support to become former-preterm lambs. Results are compared with term control lambs that were not ventilated, and between males (M) and females (F). Alveolar simplification was quantified morphometrically and stereologically at 2 mo (4 M, 4 F) or 5 mo (4 M, 6 F) corrected postnatal age (cPNA) compared with unventilated, age-matched term control lambs (4 M, 4 F per control group). These postnatal ages in sheep are equivalent to human postnatal ages of 1–2 yr and ~6 yr, respectively. Multivariable linear regression results showed that former-preterm lambs at 2 or 5 mo cPNA had significantly thicker distal airspace walls ( P < 0.001 and P < 0.009, respectively), lower volume density of secondary septa ( P < 0.007 and P < 0.001, respectively), and lower radial alveolar count ( P < 0.003 and P < 0.020, respectively) compared with term control lambs. Sex-specific differences were not detected. We conclude that moderate preterm birth and MV for ~6 days impedes completion of alveolarization in former-preterm lambs. This new model provides the opportunity to identify underlying pathogenic mechanisms that may reveal treatment approaches.

Sex-specific differences in neonatal hyperoxic lung injury

Male sex is considered an independent predictor for the development of bronchopulmonary dysplasia (BPD) after adjusting for other confounders. BPD is characterized by an arrest in lung development with marked impairment of alveolar septation and vascular development. The reasons underlying sexually dimorphic outcomes in premature neonates are not known. In this investigation, we tested the hypothesis that male neonatal mice will be more susceptible to hyperoxic lung injury and will display larger arrest in lung alveolarization. Neonatal male and female mice (C57BL/6) were exposed to hyperoxia [95% FiO2, postnatal day (PND) 1–5] and euthanized on PND 7 and 21. Extent of alveolarization, pulmonary vascularization, inflammation, and modulation of the NF-κB pathway were determined and compared with room air controls. Macrophage and neutrophil infiltration was significantly increased in hyperoxia-exposed animals but was increased to a larger extent in males compared with females. Lung morphometry showed a higher mean linear intercept (MLI) and a lower radial alveolar count (RAC) and therefore greater arrest in lung development in male mice. This was accompanied by a significant decrease in the expression of markers of angiogenesis (PECAM1 and VEGFR2) in males after hyperoxia exposure compared with females. Interestingly, female mice showed increased activation of the NF-κB pathway in the lungs compared with males. These results support the hypothesis that sex plays a crucial role in hyperoxia-mediated lung injury in this model. Elucidation of the sex-specific molecular mechanisms may aid in the development of novel individualized therapies to prevent/treat BPD.

Growth of alveoli during postnatal development in humans based on stereological estimation

Alveolarization in humans and nonhuman primates begins during prenatal development. Advances in stereological counting techniques allow accurate assessment of alveolar number; however, these techniques have not been applied to the developing human lung. Based on the recent American Thoracic Society guidelines for stereology, lungs from human autopsies, ages 2 mo to 15 yr, were fractionated and isometric uniform randomly sampled to count the number of alveoli. The number of alveoli was compared with age, weight, and height as well as growth between right and left lungs. The number of alveoli in the human lung increased exponentially during the first 2 yr of life but continued to increase albeit at a reduced rate through adolescence. Alveolar numbers also correlated with the indirect radial alveolar count technique. Growth curves for human alveolarization were compared using historical data of nonhuman primates and rats. The alveolar growth rate in nonhuman primates was nearly identical to the human growth curve. Rats were significantly different, showing a more pronounced exponential growth during the first 20 days of life. This evidence indicates that the human lung may be more plastic than originally thought, with alveolarization occurring well into adolescence. The first 20 days of life in rats implies a growth curve that may relate more to prenatal growth in humans. The data suggest that nonhuman primates are a better laboratory model for studies of human postnatal lung growth than rats.

Maternal nicotine exposure during gestation and lactation interferes with alveolar development in the neonatal lung

The aim of this study was to investigate the effect of maternal nicotine exposure during pregnancy and lactation on the development of the lungs of the offspring as a gas- exchanger. Pregnant rats received nicotine (1 mg/kg body mass day–1) subcutaneously during gestation and lactation. Nicotine administration started one day after mating and lasted until weaning on post natal Day 21. The offspring were exposed to nicotine only via the placenta and the milk of the mother. The lung tissue of the neonates was collected on post natal Days 14, 21, 35 and 42 and prepared for morphometry. The results obtained show that maternal nicotine exposure suppressed alveolarisation in the lungs of the offspring, which resulted in a reduced internal surface area available for gas exchange. The radial alveolar count as well as the number of capillaries in the septa were also significantly lower than in the control animals. It is concluded that maternal nicotine exposure had an adverse effect on the development of the gas exchange region of the lungs of the offspring that persisted at least up to Day 42 after birth.